Very ultra thin conductor layers for printed wiring boards

ABSTRACT

Disclosed is a metal-clad laminate product having a carrier film, a aqueous soluble release or parting layer deposited onto the carrier film and which can be mechanically separated from the carrier film, and an ultra thin metal layer deposited onto the parting layer. Also disclosed is a method for making the metal-clad laminate product.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority from provisional applicationSerial No. 60/047,019, filed May 13, 1997.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0002] Not applicable.

BACKGROUND OF THE INVENTION

[0003] The electronics industry continues to seek enhanced performancefrom products such as printed wiring boards used with integratedcircuits in order to meet consumer demand for higher performance, lowercost computers and electronics equipment. Driving forces within theelectronics industry include a desire for increased speed andfunctionality which requires reduced size of both components andinterconnectors. Among the means by which interconnection circuitry canbe reduced in size include the design of circuit boards that havesmaller, finer lines and spaces to increase the line density on boards.Increasing line density leads to fewer circuit layers and smaller,lighter, electronic devices.

[0004] Printed wiring board circuitry can reside on a rigid fiberglassreinforced plastic or on flexible films to which are adhered metal foilsused to form conductive circuit connections. The boards can containinterconnecting circuitry on one layer, two layers, or multiple layers.Boards with three or more layers can be manufactured using multiple twolayer boards laminated together forming a multi-layer construction, orcan be built up from a two layer board by sequentially adding dielectriclayers and circuits.

[0005] Multilayer boards are most typically manufactured by laminatingcircuitized double sided boards in a stack using sheets of thermosettingpolymers impregnated in fiberglass, known as pre-preg. Typically theouter most circuitized layers are added by using a sheet of pre-preg anda sheet of metal foil. The circuit connections on the double sided corecircuits are usually manufactured by using subtractive techniques, whilethe outer metal conductor layer is shaped in a semi-additive method. Themultiple circuit layers are electrically connected by mechanicaldrilling of holes through the board and plating with a conductive metal.

[0006] Sequential built-up boards are manufactured by laminating foilscoated with thermosetting resins to a circuitized double sided board.The coated resin layer serves as a controlled dielectric layerseparating the built-up circuit layer from the double sided circuitboard. Electrical connections between circuit layers are made by plasmaor laser drilling, followed by plating the resulting connecting hole.Circuitizing the built-up circuit is accomplished using semi-additivemethods. Build-up layers can be stacked forming a circuit with manylayers.

[0007] Circuit board designers require substrate materials on whichextremely fine lines and spaces can be formed with a high degree ofprecision. Thin metal foils are generally a preferred substrate for theformation of circuit lines on circuit boards. The use of thicker foilsresults in greater waste of metal and reduces the line density that canbe achieved. The metal films are most commonly formed byelectrodeposition. Electrodeposited copper films typically must be of adefined minimum thickness, >1 μm, to avoid holes or discontinuities.

[0008] Metal foils that are currently in use in the industry aretypically at least 5 μms in thickness. The use of thinner metal foil inprinted circuit board would allow the formation of more densely packedlines and would reduce production costs. There is a significant interestin developing methods for obtaining thin copper foils. Existing methodsfor obtaining and placing a very thin metal foil on a laminate arelimited.

[0009] U.S. Pat. No. 4,357,395 discloses a copper-clad laminate that ismade by first forming a layer of silica on an aluminum carrier and thensputtering a copper film onto the silica layer. The copper layer is thenlaminated to a substrate, and the carrier and silica layer aremechanically stripped away, leaving the copper layer exposed. Theexamples disclosed that copper films 5-10 μms in thickness were obtainedby this method.

[0010] The method disclosed in U.S. Pat. No. 4,357,395 is not suitablefor the manufacture of copper-clad laminates having an very ultra thin(0.1-0.3 μm) copper foil, because very ultra thin foils are susceptibleto picking when the carrier and silica layers are mechanically removed.

[0011] U.S. Pat. No. 4,431,710 reveals an aluminum carried copper foilwhere the copper was deposited onto the aluminum foil using vapordeposition at temperatures between about 100° C. and 250° C. Copper filmof 5 μms in thickness was demonstrated. After lamination to a substrate,the aluminum carrier is removed with a peel force of 0.5 lbs./in. to 2.0lbs./in. The disclosure discusses the variability in the peel strengthexperiences by this method. The high peel strengths and variabilitywould be detrimental to very ultra thin foils of less than 1 μm inthickness. In addition, the exemplified foil is shown to have asignificant impact on peel strength, dependent on contaminants.

[0012] U.S. Pat. No. 5,262,247 describes a foil consisting of a coppercarrier layer, a chromate parting layer, a copper-nickel alloy layer,and finally a thin copper foil layer. Upon lamination the copper carrierplus chromate layer is removed. The resulting metallized substraterequires etching of the copper-nickel layer to reveal the copper layer.It is emphasized and claimed that the thin copper foil layer must be 1μm to 10 μms in thickness. Below 1 μm copper thickness is not used dueto the etching step required to remove the copper-nickel layer. Etchingthe copper-nickel layer will also etch the underlying copper layer.

[0013] What is needed in the art is a method for obtaining very ultrathin metal foil laminates for the manufacture of printed circuit boards.

BRIEF SUMMARY OF THE INVENTION

[0014] It is the object of the present invention to provide a metal-cladlaminate for use in the manufacture of printed circuit boards, thelaminate having a very ultra thin metal foil that will support theformation of very fine lines and spaces thereon.

[0015] Another object of the present invention is to provide a methodfor large scale production of a metal-clad laminate for the manufactureof printed circuit boards, the laminate having a very ultra thin metalfoil that will support the formation of very fine lines and spaces.

[0016] It is a further objective of the invention to supply a foil foruse in multi-layer and built-up circuit boards, the foil being veryultra thin to enable fine line circuit formation.

[0017] The present invention is a metal-clad laminate for themanufacture of printed circuit boards, the laminate having a very ultrathin metal foil that is at most about one μm in thickness.

[0018] The present invention is also a method of manufacturing ametal-clad laminate for the manufacture of printed circuit boards, thelaminate having a very ultra thin metal foil that is at most about oneμm in thickness.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0019]FIG. 1 is a cross-sectional illustration of a metal-clad laminateintermediate constructed in accordance with the present invention.

[0020]FIG. 2 is a cross-sectional illustration of an alternativemetal-clad laminate constructed in accordance with the presentinvention.

[0021] FIGS. 3-6 illustrate cross-sectional views of alternativeembodiments of the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0022] The present invention is directed toward very ultra thin metalconductive layers which are formed by vapor deposition or sputtering ofthe conductive metal on a polymeric or metal carrier film which has beencoated with an organic polymeric release agent. The metal conductivelayer can then be bonded to a printed wiring board substrate, such as anepoxy-based laminate. Then the carrier film can be separated from thepolymeric release agent, leaving the metal conductive layer bonded tothe substrate. Using this approach, conductive metal layers in the rangeof 0.005 μm to 1.0 μm (50 to 10,000 Angstroms) become practical.

[0023] In accordance with the present invention, a metal-clad laminateproduct for use in the manufacture of printed circuit boards can be madeincluding a polymer or metal foil carrier layer, a polymeric partinglayer formed on the carrier film, a very ultra thin metal layer formedon the release agent layer. Shown in FIG. 1 is a metal-clad intermediate10 made in accordance with the present invention. The intermediate 10 ismade up of a carrier film 11 to which is applied a polymeric releaseagent layer 12, onto which is applied a very ultra thin conductive metallayer 13.

[0024] Shown in FIG. 2 is an alternative embodiment of such a metal cladlaminate product here designated 20. In the embodiment of FIG. 2, acarrier film 21 has applied to it a polymeric release agent layer orparting layer, 22. Onto the release agent layer 22 is deposited aprimary very ultra thin conductive metal layer 23. On top of the primarymetal layer 23 is a secondary metal layer 24, also preferably formed bysputtering or vapor deposition.

[0025] Shown in FIG. 3 is an alternative embodiment metal cladintermediate 30 is illustrated which includes a carrier film 31, arelease agent or parting layer 32, and a primary very ultra thinconductive metal layer 33. Also deposited on the metal layer 33 is anadhesion layer 35.

[0026] Shown in FIG. 4 is another embodiment which includes in a metalclad intermediate 40, a carrier film 41, a release agent layer 42, avery ultra thin primary metal layer 43, a secondary metal layer 44 andan adhesive layer 45.

[0027] In FIG. 5 an alternative metal clad intermediate 50 is shownwhich includes a carrier film 51, a release agent layer 52, a very ultrathin primary metal layer 52, and an adhesion layer 54. This embodimentalso includes two layers of circuit board resin laminate material, orpre-preg, designated here 56 and 57.

[0028] Shown in FIG. 6 is another alternative metal clad intermediate 60including a carrier film 61, a release agent layer 62, a primary metallayer 63, a secondary metal layer 64, an adhesion layer 65, and twolayers of resin laminate materials 66 and 67.

[0029] These alternative embodiments are illustrated and discussed toexemplify the wide variation in selection and number of layers that canbe used to assemble such intermediates.

[0030] Preferably, the carrier film comprises a flexible, dimensionallystable material with good tear and chemical resistances. The carrierfilm should be able to tolerate above-ambient temperatures. Preferably,the carrier film is made of a material having low absorbed moisture andresidual solvent, because water and solvents can interfere with themetallization step. Suitable materials include polymeric film or metalfoils. A metal foil is preferred because metal foils tend to have hightensile strength at elevated temperatures, low absorbed moisture, andlow residual solvent.

[0031] The carrier film employed in the examples below was anelectroplated copper foil or a polyimide film. Other metal foils thatwould make suitable carrier films include rolled or electrodepositedmetal and metal alloys including steel, aluminum (Alcoa, AllFoils), andcopper (Gould Inc., Oak Mitsui Inc.). It is expected that certainpolymeric films would be suitable for the practice of the presentinvention. Examples of suitable polymeric films include polyesters suchas poly-ethylene terephthalate, poly-butylene terephthalate andpolyethylene naphthalate (Kaladex®, ICI America), poly-propylene,polyvinyl fluoride (Tedlar®, DuPont), polyimide (Kapton®, DuPont;Upilex®, UBE Industries), and nylon (Capran®, AlliedSignal).

[0032] The release agent layer (11 in FIG. 1, 21 in FIG. 2, 31 in FIG.3, etc.) is used to facilitate removal of the carrier film from the veryultra thin metal layer. In order to avoid the problem of picking, whichresults in incomplete transfer of the very ultra thin metal foil to thesubstrate under lamination, the release agent layer is designed to peelat the interface between the parting layer and film carrier. The partinglayer is subsequently removed with the aid of a plasma, an oxidatingenvironment, intense light, or an appropriate solvent. Preferably, thelayer is removed by washing with a solvent, most preferably an aqueoussolution. In methods that lack a release agent layer, and in methodsthat employ a release agent layer that peels at the interface betweenthe parting layer and the very ultra thin metal layer, incompletetransfer of the metal of the very ultra thin metal foil to the substratecommonly occurs.

[0033] The parting layer (12 in FIG. 1, 22 in FIG. 2, etc.) is made of apolymeric material. Preferably, the parting layer is an aqueous-solublematerial to facilitate its convenience removal from the very ultra thinmetal layer. Because photo resists are developed in an alkalineenvironment, it would be most preferable to use a parting layer that issoluble in an alkaline aqueous solution. A useful polymer is one that isof a good film-forming material. The polymer can be coated from waterwith the aid of a volatile base such as ammonium hydroxide to aidsolubility. Optionally, the parting layer comprises a water-solublesurfactant to improve solution wetting properties, and to control dryingdefects.

[0034] As detailed in the examples below, one useful release agent, orparting layer, is applied as a formulation comprising apolyvinylpyrrolidone (PVP) polymer, a surfactant, and water. The wetweight composition of the parting layer formulation described in theexamples is 10% PVP and 0.5% surfactant. It is expected thatformulations containing PVP in the range of from about 1% PVP to about50% PVP, and surfactant in the range of from about 0% surfactant toabout 5% surfactant would also be suitable for the practice of thepresent invention. Preferred PVPs for use in the present invention havea molecular weight in the range of about 10,000 to about 5,000,000. Itis reasonable to expect that a release agent layer comprising a polymersuch as acid modified acrylic polymers, acrylic copolymers, urethanes,and polyesters, carboxylic acid functional styrene acrylic resins (S. C.Johnson Wax, Joncryl®), polyvinyl alcohols (Air Products & Chemicals,Airvol®), and cellulose based polymers could be successfully employed inthe practice of the present invention. Other suitable water solublesurfactants that could be used to in the parting layer of the presentinvention include alkylarylpolyether alcohols (Rohm & Haas, Triton®X100), glycerin, ethoxylated castor oil (CasChem Inc., Surfactol® 365),and fluoroaliphatic polymeric esters (3M Corporation, Fluorad® 430). Therelease agent layer formulation is applied in an amount sufficient toachieve a dry weight of from about 10 mg/ft² to about 400 mg/ft², about0.1 μm to 10 μm in thickness. Preferably, the release agent layerformulation is applied in an amount sufficient to achieve a dry weightof from about 100 mg/ft² to about 400 mg/ft², about 1 μm to 4 μm inthickness.

[0035] As described in detail in the examples, a thin primary conductivemetal layer (13 in FIG. 1, 23 in FIG. 2, etc.) can be deposited onto theparting layer by sputtering using a Desk III sputtering unit. It isexpected that any sputtering or vapor deposition method known in the artmay be successfully used in this invention. The primary metal layer isused as a plating seed layer for subsequent circuit formation. In theexamples below, the metal layer was made from gold, chrome, or copper.Other suitable metals include, but not limited to, tin, nickel,aluminum, titanium, zinc, chromium-zinc alloy, brass, bronze, and alloysof the same. The metal layer may be made from a mixture of suitablemetals. The primary layer is from about 0.005 μm (50 Angstroms) to about1.0 μm (10,000 Angstroms) in thickness. Most preferably the primarylayer has thickness of from about 0.1 μm to about 0.3 μm (1000 to about3000 Angstroms).

[0036] Optionally, a secondary metal layer (such as layer 24 in FIG. 2,44 in FIG. 4, or 64 in FIG. 6) may be employed to protect the primarylayer from oxidation, to increase adhesion during lamination, or to actas a barrier to metal migration. The secondary layer may be from about0.001 μm (10 Angstroms) to about 0.1 μm (1000 Angstroms) in thickness.Most preferably the secondary layer has thickness of from about 0.01 μm(100 Angstroms) to about 0.03 μm (300 Angstroms). To form the secondarymetal layer, a layer of zinc, indium, tin, cobalt, aluminum, chrome,nickel, nickel-chrome, brass, or bronze is deposited on the first metallayer. Other suitable metals include magnesium, titanium, manganese,bismuth, molybdenum, silver, gold, tungsten, zirconium, antimony, andchromium-zinc alloys. The secondary metal layer prevents the metal inthe first metal layer from oxidizing after removal from the metallizingchamber, and increases adhesion to thermosetting resin systems.

[0037] Optionally, an adhesion layer (e.g. 35 in FIG. 3, 45 in FIG. 4,etc.) can be applied to the metal layer. The adhesion layer may beemployed in order to increase the bond between the metal layers and thesubstrate layers following lamination. The adhesion layer may beorganic, organometallic, or inorganic compounds, and applied to athickness of 0.0005 μm (5 Angstroms) to 10 μm (100,000 Angstroms).Multiple layers may be used such as an organometallic layer followed byan organic layer. Typically when an organometallic layer is used, suchas a silane, the coating will be from 0.0005 μm (5 Angstroms) to 0.005μm (500 Angstroms) in thickness. When using organic adhesion layers,such as thermoplastics, thermosetting polymers, or mixtures, the coatingwould be 0.1 μm (1000 Angstroms) to 10 μm (100,000 Angstroms) inthickness.

[0038] Useful organometallic compounds include materials based onzirconium, titanium, and silicon. Silicon based organometallics, knownas silanes or coupling agents, are widely used and available. Thecoupling agent may be applied neat or applied after dissolving it in anappropriate solvent. Suitable coupling agents typically have asilane-hydrolyzable end group with alkoxy, acyloxy, or aminefunctionality, and an organofunctional end group. The hydrolyzable endgroup reacts with the metal surface while the organofunctional groupbonds to the substrate layer to which the metal is laminated. Couplingagents can be subjected to a hydrolysis reaction prior to coating ifdissolved in an acidic medium. Useful coupling agents include compoundssuch as N-(2-aminoethyl)-3-aminopropyltrimethoxy silane (Dow Corning,Huls America Inc.) and 3-Glycidoxypropyltrimethoxy silane (Dow Corning,Huls America Inc.). Organic adhesion layers consisting ofthermoplastics, thermosetting polymers, or mixtures are appropriateadhesion layers. These adhesives can be based on polyimide resins, epoxyresins, polyester resins, acrylic resins, butadiene rubbers, and thelike. One useful adhesive consisting of a polyester epoxy system isavailable (Cortaulds, Z-Flex™).

[0039] Resin layers can be applied to the metal layer or to the adhesivelayer (if present) in uses where a controlled dielectric thickness isrequired. Such uses include built up technologies. Typically the resinsare thermosetting systems that are coated from an appropriate solvent.After drying, the resins can be cured to a semi-cured state ifadditional cure is required before lamination to a circuit board. Asingle semi-cured resin layer can be used. Preferably, two resin layersare used where the first resin layer down (primary layer) is cured to agreater extent than the second resin layer. The first resin layer servesas a controlled dielectric spacing layer and has a thickness of fromabout 5 to about 500 μms, preferably from about 20 to about 50 μms.Appropriate resin systems include (but not limited to): epoxy resinscured by phenolic or dicyandiamide hardeners, cyanate esters,bismaleimides, and polyimide systems. The second layer can have adifferent composition than the primary layer; however, to attain goodinterlayer adhesion, it is preferable that the composition of the secondlayer is similar to that of the first resin layer. The second resinlayer serves as an adhesion layer and as a void filling layer duringlamination and has a thickness between 5 and 500 μms, preferably between20 and 50 μms.

[0040] By “laminating under suitable lamination conditions” it is meantlaminating under appropriate conditions of temperature and pressure fora suitable period of time to adhere the layers together for practicaluse in making a circuit board laminate.

[0041] The following nonlimiting examples are intended to be purelyillustrative.

EXAMPLE 1

[0042] Upilex® 50 μm polyimide film was obtained from the Ube Industriesfor use as the carrier film. 0.15 μm (1500 Angstroms) of copper wassputtered coated, followed by 0.01 μm (100 Angstroms) of a nickel-chromealloy. The sample was pressed to make a circuit board laminate. Fourlayers of an FR-4 pre-preg known as FR406 (AlliedSignal) was placed on aglass reinforced Teflon® sheet. Under the sheet was a stainless steelpress plate. The above construction was placed metal side down on theFr406 pre-preg. A second layer of glass reinforced Teflon® sheet wasplaced on the top and covered with a second stainless steel press plate.The stack was placed in a pre-heated press at 350° F. and pressed for1.2 hours at 50 psi. The film was attempted to be peeled, but wasdifficult. Peel strength measured at an angle of 180° and found to varybetween 1-5 lbs./in. Sections of the metal coating approximately 100 μmin size did not transfer and were left on the film. The metal coating“picked”. The above was attempted a second time, and was found the metalcoating would not peel from the film carrier. Metal adhesion to the filmwas high enough to cause the film to tear during a peel attempt.

EXAMPLE 2

[0043] A sample of 1 oz. electroplated copper foil was obtained fromGould Inc. for use as a carrier film. A release agent layer was formedby coating parting layer formulation P1 (Table 1) onto the coppercarrier layer using a No. 18 wire-wound rod. Following application tothe carrier film, the release agent layer was dried at 160° C. for about2 minutes. The coating was clear. A gold metal conductive layer wassputtered onto the clear parting layer using a Desk III sputtering unitwith air as the processing gas. Gold was deposited for 3 minutes.Examination an edge of the gold coating by microscopy revealed that agold layer of approximately 0.3 μm (3000 Angstroms) in thickness wasdeposited.

[0044] The sample was pressed to make a circuit board laminate. Fourlayers of an FR-4 epoxy based pre-preg known as FR406 (AlliedSignal) wasplaced on a glass reinforced Teflon® sheet. Under the sheet was astainless steel press plate. The above construction was placed metalside down on the FR406 pre-preg. A second layer of glass reinforcedTeflon® sheet was placed on the top and covered with a second stainlesssteel press plate. The stack was placed in a pre-heated press at about350° F. and pressed for about 1.2 hours at 50 psi. After cooling to roomtemperature, the copper carrier film peeled easily revealing the partinglayer transferred completely with the metal coating. Washing the surfacein warm water removed the release agent layer and revealed a shiny metalsurface. TABLE 1 Composition of parting layer formulation P1. ComponentSource Amount Polyvinylpyrrolidone, ISP Technologies  5.00 g PVP-K90Surfactol 365 CasChem  0.025 g Water 44.975 g

EXAMPLE 3

[0045] A sample of 1 oz. electroplated copper foil was obtained fromGould Inc for use as the carrier film. A release agent layer was formedby coating formulation P1 (Table 1) onto the copper carrier film using aNo. 18 wire-wound rod. Following application to the carrier film, theparting layer was dried at 160° C. for about 2 minutes. The coating wasclear. A gold metal layer was sputtered onto the clear parting layerusing a Desk III sputtering unit with air as the processing gas. Goldwas deposited for 3 minutes. Examination an edge of the gold coating byvisible microscopy revealed that a gold layer of approximately 0.3 μm(3000 Angstroms) in thickness was deposited. A first resin layer wasmade by coating formulation R1 (Table 2) onto the gold layer using a No.18 wire-wound rod. The first resin later was dried at about 50° C. forabout 1 hour, then held at about 65° C. for about 1 hour, and finallycured at about 170° C. for about 6 minutes. A second resin layer wasmade by coating formulation R1 onto the first layer using a No. 18wire-wound rod. The second resin was dried using the same dryingconditions that were employed in for the first resin layer.

[0046] Four layers of an FR-4 pre-preg known as FR406 (AlliedSignal)were placed on a glass-reinforced Teflon® sheet. Under the sheet was astainless steel press plate. A second layer of glass-reinforced Teflon®sheet was placed on the top and covered with a second stainless steelpress plate. The stack was placed in a pre-heated press at 350° F. andpressed for 1.2 hours at 50 psi. After cooling to room temperature, thestack was broken down and the glass reinforced Teflon® sheet removedrevealing and unclad laminate. The above construction was placed on topof the unclad laminate with resin side contacting the laminate. A glassreinforced Teflon® sheet covered the construction followed by astainless steel press plate. A second stainless steel press plate wasplaced under the laminate. The stack was placed in a pre-heated press at350° F. and pressed for 1.2 hours at 50 psi. After cooling to roomtemperature, the copper carrier film was peeled easily revealing theparting layer transferred completely with the metal coating and resinlayers. Washing the surface in warm water removed the parting layer andrevealed a shiny metal surface. TABLE 2 Composition of resin formulationR1. Component Source Amount Epon 1031A70 Shell Chemical 1.98 g DER732Dow Chemical 5.67 g PKHS-40 Phenoxy 18.16 Associates Ciba 1138A85 CibaGeigy 15.91 g Quatrex 6410 Dow Chemical 22.69 BT2110 Mitsubishi Gas &34.97 g Chemical DMF 7.37 g Methyl Ethyl Ketone 46.13 g

[0047] TABLE 3 Composition of parting layer formulation P2. ComponentSource Amount Polyvinylpyrrolidone, PVP-K120 ISP Technologies  5.00 gSurfactol 365 CasChem  0.025 g Water 44.975 g

[0048] This formulation P2 differs from P1 in the choice of PVP K120,which has a weight average molecular weight of 2,900,000. The PVP usedin the Formulation P1 was PVP K90, which has a weight average molecularweight of 1,270,000. Higher molecular weight is desirable for coatingand film formation while lower molecular weight is desirable forincreased layer solubility.

EXAMPLES 4-7

[0049] A sample of ½ oz. electroplated high temperature elongationcopper foil was obtained from Oak-Mitsui for use as a carrier film.Release agent formulation P2 was coated on the carrier film using a No.18 wire-wound rod and dried at 160° C. for 2 minutes. The coating wasclear and measured to be 250 mg/ft². Different metal layer combinationsare sputter deposited onto the P2 coating using argon as the processinggas: Metal Layer-(s) Comments Example 4 Gold, 3000 Angstroms Example 5Chrome, 100-200 Angstroms Example 6 Copper, 3000 Angstroms, The thinchrome layer followed by, Chrome, 100 is used as a Angstroms passivationlayer between the copper and the laminate. Example 7 Copper, 1500Angstroms, The thin zinc layer is followed by, Zinc, 50-100 used as apassivation Angstroms layer between the copper and the laminate. Whenthe construction is heated in the press, the zinc alloys with a thinlayer of the copper forming brass

[0050] The constructions are of the form illustrated in FIG. 1.

[0051] An adhesion layer consisting of a silane was coated on the metallayer in example 6 and 7. A solution of Gamma-glycidoxypropyl trimethoxysilane was made to 0.5% in a mixture of methanol and water, where themethanol was 90% and the water was 10%. The solution was coated on themetal surface and dried at 90° C. for 1 minute.

[0052] Each sample was pressed to make a circuit board laminate. Fourlayers of an FR-4 pre-preg known as FR406 (AlliedSignal) was placed on aglass reinforced Teflon® sheet. Under the sheet was a stainless steelpress plate. The above construction was placed metal side down on theFR406 pre-preg. A second layer of glass reinforced Teflon® sheet wasplaced on the top and covered with a second stainless steel press plate.The stack was placed in a pre-heated press at 350° F. and pressed for1.2 hours at 50 psi. After cooling to room temperature, the coppercarrier film peeled easily revealing the parting layer transferredcompletely with the metal coating. Washing the surface in warm waterremoved the parting layer and revealed the shiny metal surface of theconductive layer.

[0053] The peel force required to remove the carrier layer was measuredat an angle of 180° on Example 6 and Example 7. The peel force wasdetermined to be very low and was repeatable. Example 6 was measured at0.025 lbs./in. while Example 7 was measured at 0.015 lbs./in.

EXAMPLE 8

[0054] Upilex® 50 μm polyimide film was obtained from the UbeIndustries. Formulation P2 was coated on the carrier film using a No. 18wire-wound rod and dried at 160° C. for 2 minutes. The coating was clearand measured to be 250 mg/ft². A gold metal layer was sputtered on theclear coating using a Desk III sputtering unit with air as theprocessing gas. Gold was deposited for 3 minutes. Examining an edge ofthe gold coating using a visible microscope revealed 0.3 μm (3000Angstroms) of gold was deposited.

[0055] The sample was pressed to make a circuit board laminate. Fourlayers of an FR-4 pre-preg known as FR406 (AlliedSignal) was placed on aglass reinforced Teflon® sheet. Under the sheet was a stainless steelpress plate. The above construction was placed metal side down on theFR406 pre-preg. A second layer of glass reinforced Teflon® was placed onthe top and covered with a second stainless steel press plate. The stackwas placed in a pre-heated press at 350° F. and pressed for 1.2 hours at50 psi. After cooling to room temperature, the polyimide film peeledeasily revealing the parting layer transferred completely with the metalcoating. Washing the surface in warm water removed the parting layer andrevealed a shiny metal surface.

EXAMPLE 9

[0056] Upilex® 50 μm polyimide film was obtained from the Ube Industriesfor use as the carrier film. Release formulation P2 is coated on thecarrier film using a No. 18 wire-wound rod and dried at 160° C. for 2minutes. The coating was clear and measured to be 250 mg/ft². A coppermetal layer was vapor deposited on the clear coating using a CVE vacuumChamber manufactured by CVC Products, Inc. Copper was deposited forapproximately 4 minutes.

[0057] An adhesion layer consisting of a silane was coated on the metallayer. A solution of Gamma-glycidoxypropyl trimethoxy silane was made to0.5% in a mixture of methanol and water, where the methanol was 90% andthe water was 10%. The solution was coated on the metal surface anddried at 90° C. for 1 minute.

[0058] The sample was pressed to make a circuit board laminate. Sixlayers of an FR-4 pre-preg known as FR408 (AlliedSignal) was placed on aglass reinforced Teflon® sheet. Under the sheet was a stainless steelpress plate. The above construction was placed metal side down on theFR408 pre-preg. A second layer of glass reinforced Teflon® sheet wasplaced on the top and covered with a second stainless steel press plate.The stack was placed in a pre-heated press at 350° F. and pressed for1.2 hours at 50 psi. After cooling to room temperature the polyimidefilm peeled easily revealing the parting layer transferred completelywith the metal coating. Washing the surface in warm water removed theparting layer and revealed a shiny metal surface.

[0059] The peel force required to remove the carrier layer was measuredat an angle of 180° and found to be very low at 0.010 lbs./in. and to behighly repeatable.

EXAMPLE 10

[0060] A sample of the ½ oz. electroplated high temperature elongationcopper foil was obtained from Oak-Mitsui for use as a carrier film.Release formulation P2 was coated using a No. 18 wire-wound rod anddried at 160° C. for 2 minutes. The coating was clear and measured to be250 mg/ft². A copper metal layer was vapor deposited on the clearcoating using a CVE vacuum Chamber manufactured by CVC Products, Inc.Copper was deposited for approximately 4 minutes.

[0061] The sample was pressed to make a circuit board laminate. Fourlayers of an FR-4 pre-preg known as FR406 (AlliedSignal) was placed on aglass reinforced Teflon® sheet was placed on the top and covered with asecond stainless steel press plate. The stack was placed in a pre-heatedpress at 350° F. and pressed for 1.2 hours at 50 psi. After cooling toroom temperature, the copper carrier film peeled easily revealing theparting layer transferred completely with the metal coating. Washing thesurface in warm water removed the parting layer and revealed a shinymetal surface.

It is claimed:
 1. A metal-clad laminate product for the manufacture ofprinted circuit boards, the product comprising: (a) a carrier film; (b)a release agent layer covering a surface of the carrier film, therelease agent layer comprising an aqueous soluble polymer, the releaseagent layer being capable of being mechanically peeled from the carrierlayer; and (c) a conductive metal layer deposited onto the release agentlayer, the metal layer having a thickness of at most 10,000 Angstroms.2. The laminate product of claim 1 wherein the release agent layercomprises polyvinyl pyrrolidone.
 3. The laminate product of claim 2wherein the polyvinyl pyrrolidone in the release layer has a molecularweight of between 10,000 and 5,000,000.
 4. The laminate product of claim1 wherein the carrier layer is a polymeric film.
 5. The laminate productof claim 1 wherein the carrier layer is a metal foil.
 6. The laminateproduct of claim 1 further comprising an adhesive layer on the metallayer on its side opposite from the release agent layer.
 7. The laminateproduct of claim 1, further comprising at least one semi-cured resinlaminate layer adhered to the conductive metal layer.
 8. A metal-cladlaminate intermediate product for use in the manufacture of printedcircuit boards, the product comprising: (a) a carrier film; (b) arelease agent lay covering one surface of the carrier film, the releaseagent layer comprising an organic polymer which facilitates the releaselayer being mechanically peeled from the carrier film; (c) a primaryconductive metal layer deposited onto the release layer, the metalconductive layer being no thicker that about 10,000 Angstroms; and (d) asecondary metal layer deposited on the primary metal layer, thesecondary layer having a thickness of at most 300 Angstroms.
 9. Thelaminate product of claim 8 wherein the release agent layer comprisespolyvinyl pyrrolidone.
 10. The laminate product of claim 9 wherein thepolyvinyl pyrrolidone in the release layer has a molecular weight ofbetween 10,000 and 5,000,000.
 11. The laminate product of claim 8wherein the carrier layer is a polymeric film.
 12. The laminate productof claim 8 wherein the carrier layer is a metal foil.
 13. The laminateproduct of claim 8 further comprising an adhesive layer on the metallayers on the side opposite from the release agent layer.
 14. Thelaminate product of claim 8 further comprising at least one semi-curedresin layer adhered to the conductive layer.
 15. A method for making ametal-clad laminate product comprising the steps of: (a) providing acarrier film of dimensionally stable material; (b) depositing onto thecarrier layer a release agent layer, the release agent layer comprisingan aqueous soluble polymer, the release agent layer being capable ofbeing mechanically peeled from the carrier layer; (c) forming aconductive metal layer on the release agent layer, the metal layercomprising a metal selected from the group consisting of copper, gold,chrome, tin, nickel, aluminum, titanium, zinc, and mixtures thereof, themetal layer having a thickness of at most about 10,000 Angstroms; (d)bonding the metal layer to a resin circuit board laminate layer; and (e)peeling the carrier film from the metal layer without damaging the metallayer attached to the circuit board laminate layer.
 16. A method asclaimed in claim 15 wherein the release agent layer is formed ofpolyvinyl pyrrolidone.
 17. A method for making a metal-clad laminateproduct comprising the steps of: (a) providing a carrier film ofdimensionally stable suitable material; (b) depositing onto the carrierfilm a release agent layer, the release agent layer comprising anaqueous soluble polymer, the release agent layer being capable of beingmechanically peeled from the carrier layer; (c) forming a conductivemetal layer on the release agent layer, the metal layer comprising ametal selected from the group consisting of copper, gold, chrome, tin,nickel, aluminum, titanium, zinc, and mixtures thereof, the metal layerhaving a thickness of at most about one μm; (d) applying a first oneresin circuit board laminate layer to the metal layer and semi-curingthe resin; (e) applying a second resin circuit board laminate layer tothe first resin circuit board laminate layer and semi-curing the secondlayer while additionally curing the first layer; and (f) removing thecarrier film without damaging the conductive metal layer.
 18. A methodas claimed in claim 17 wherein the release agent layer is polyvinylpyrrolidone.